The application and use of the essentially ubiquitous one-dimensional bar code are well established. Such bar code symbols are provided as images having two physical dimensions, however the bar code includes information coded in only one dimension (e.g., left to right). While such one-dimensional bar codes have found innumerable applications, their usefulness is ultimately limited by amount of information which can be encoded in each such bar code.
Two-dimensional bar codes, enabling encoding of greatly increased quantities of information, have now been proposed. FIG. 1 shows an example of a two-dimensional bar code. Such bar codes typically include a few to many rows of coded data grouped in parallel alignment between start and stop patterns which bound the group of rows of coded data transversely to the rows. Coded row data, also typically included in the bar code, may provide information identifying and distinguishing individual rows of data, information regarding the data coded in such a row, information enabling error correction, etc. While such two-dimensional bar code images also have two dimensions, they differ from one-dimensional bar codes in providing two-dimensions of coded information. An example of a two-dimensional bar code is given in the present inventor's prior U.S. Pat. No. 5,113,455, entitled "System For Encoding Data in Machine Readable Graphic Form", issued May 12, 1992. Another example, described as the "PDF417" symbol, has been proposed in a PDF417 Specification, dated October 18, prepared by the present inventor for Symbol Technologies, Inc. and submitted for review by the Technical Symbology Committee of the Automatic Identification Manufacturers, Inc.
One-dimensional bar codes have come into wide usage on the basis of permitting application to supermarket items, vehicles, inventory parts, etc., of an image representing a multi-digit identifying number which is readily machine-readable. A variety of devices and applications of technology using lasers or charge coupled devices, for example, have been made available and are in wide use for reading such bar codes. On the one hand, two-dimensional bar codes make possible a wide-variety of new uses and applications in which a much wider range of information and data may be encoded and distributed by mail, facsimile transmission, etc., alone or in combination with other graphic or textural images, as well as being affixed to products, vehicles and inventory items, for example. On the other hand, two-dimensional bar codes require more complex capabilities for accurately reading the greatly increased amount of encoded data. Such requirements can be accommodated by use of sophisticated scanning equipment able to provide electronic output signals representing pixel data which is synchronized both on a pixel-by-pixel basis and also on a scan-by-scan basis. Availability of such signals enables reconstruction of a high-resolution image of the bar code, including accurate registration of the pixel elements of the image in two dimensions (e.g., horizontally and vertically). With use of such a high resolution scanner device or equipment, two-dimensionally synchronized image signals can be provided, so as to permit decoding of the bar code. Actual location and orientation of the bar code image within the scanned image (assuming the scanning device, as a practical matter, actually scans a somewhat larger image area which includes at least one bar code image) may entail a substantial data processing capability. In addition, the decoding of the bar code using the bulk of high-resolution image data resulting from use of such a high-resolution scanner may require additional data processing capabilities of a fairly extensive nature.
The result of the foregoing is that extension of use of two-dimensional bar codes to all logical applications may be restricted on an economic basis in the absence of comparatively simple devices capable of implementing the required scanning and decoding of the bar code images both reliably and economically.
It is therefore an object of this invention to provide hand-holdable devices capable of both scanning and decoding two-dimensional bar codes to provide a decoded output.
It is a further object to provide scanner/decoder devices which are reliable and economical in utilizing a single line of charge coupled devices or other image sensing elements, without reliance upon location tracking data, so that no tracking ball or roller device is included.
Further objects of the invention are to provide scanner/decoder devices enabling reliable operation with a scanning function providing image signals of limited image resolution and synchronization, and scanner/decoder devices operating with a reduction in image signal processing as a result of redundant scan cancellation.
Additional objects are to provide new and improved devices which accomplish both scanning and decoding of one-dimensional and two-dimensional bar codes and similar coded images, and particularly such devices which are compact, economical and readily hand operable.